def imag(z):
    """
    Returns the imaginary part of a complex number or a matrix of complex numbers.
    
    Args:
        z (complex or list of lists of complex): The complex number or matrix of complex numbers to compute the real part of.

    Returns:
        float or list of lists of float: The real part of the input number or matrix of numbers.

    """
    if isinstance(z, complex):
        return z.imag
    elif isinstance(z, list) or isinstance(z, tuple):
        return [imag(elem) for elem in z]
    elif isinstance(z, (int, float)):
        return 0
    elif isinstance(z, (list, tuple)):
        return [imag(elem) for elem in z]
    else:
        # Raise TypeError for unsupported input types
        raise TypeError("Input type not supported.") 

# Test case 1: Input is a single complex number
z1 = 3 + 4j
assert imag(z1) == 4

# Test case 2: Input is a list of complex numbers
z2 = [2 + 3j, 4 + 5j, 6 + 7j]
assert imag(z2) == [3, 5, 7]

# Test case 3: Input is a nested list of complex numbers
z3 = [[1 + 2j, 3 + 4j], [5 + 6j, 7 + 8j]]
assert imag(z3) == [[2, 4], [6, 8]]

# Test case 4: Input is a tuple of complex numbers
z4 = (3 + 4j, 5 + 6j, 7 + 8j)
assert imag(z4) == [4, 6, 8]

# Test case 5: Input is a nested tuple of complex numbers
z5 = ((2 + 3j, 4 + 5j), (6 + 7j, 8 + 9j))
assert imag(z5) == [[3, 5], [7, 9]]

# Test case 6: Input is an integer
z6 = 10
assert imag(z6) == 0

# Test case 7: Input is a float
z7 = 3.1415
assert imag(z7) == 0

# Test case 8: Input is a string (unsupported input type)
z8 = "hello"
try:
    imag(z8)
except TypeError:
    pass
else:
    raise AssertionError("Expected TypeError for unsupported input type")
